Presently, the so-called memory vehicle seat slides can be classified into two groups which are:
manual memory slides whose position which is previously chosen is respected upon a return of the seat after a given displacement. The mechanism which is involved includes at least one rack for setting the seat position in length, and a second mechanism with a second rack, the mobile portion of the second slide being provided for forming the memory; this mechanical system is bulky and not very accurate.
electrically controlled memory slides whose position which is chosen after each displacement of the seat is restored by using an electronic central unit; the construction is then rather heavy, bulky and costly.
In cases where the seat slides do not include a chosen position memory, one has in fact to carry out after each displacement of the seat a new complete setting of the most convenient position of the seat for the user.
However, for two-door vehicles, it is more and more necessary to have, for each front seat, longitudinal setting slides including memories for the positioning of the seat and enabling a rapid temporary displacement of the seat in order to permit the ear passengers of a two-door vehicle to get in or out of the vehicle, and then to bring the front seat involved back to the prior position.
It should be reminded that in case of a so-called manual memory slide, a setting in position of the seat as well as a setting of the memory is dependent on the pitch of the serrations or of the pitch of each slide rack; therefore, the position of the seat can be obtained only with an approximate setting taking into account the pitch of the serrations or the pitch of the rack.
In the case of an electrically controlled memory slide, the positioning is very precise and can be called of a micro-millimetric controlled type.